A debug code assert needed to be behind the new optimize_constructed_arrays flag.

src/x64/builtins-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1506 matching lines @@
 
     // Initial map for the builtin Array function should be a map.
     __ movq(rcx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
     // Will both indicate a NULL and a Smi.
     STATIC_ASSERT(kSmiTag == 0);
     Condition not_smi = NegateCondition(masm->CheckSmi(rcx));
     __ Check(not_smi, "Unexpected initial map for Array function");
     __ CmpObjectType(rcx, MAP_TYPE, rcx);
     __ Check(equal, "Unexpected initial map for Array function");
 
-    // We should either have undefined in ebx or a valid jsglobalpropertycell
-    Label okay_here;
-    Handle<Object> undefined_sentinel(
-        masm->isolate()->factory()->undefined_value());
-    Handle<Map> global_property_cell_map(
-        masm->isolate()->heap()->global_property_cell_map());
-    __ Cmp(rbx, undefined_sentinel);
-    __ j(equal, &okay_here);
-    __ Cmp(FieldOperand(rbx, 0), global_property_cell_map);
-    __ Assert(equal, "Expected property cell in register rbx");
-    __ bind(&okay_here);
+    if (FLAG_optimize_constructed_arrays) {
+      // We should either have undefined in ebx or a valid jsglobalpropertycell
+      Label okay_here;
+      Handle<Object> undefined_sentinel(
+          masm->isolate()->factory()->undefined_value());
+      Handle<Map> global_property_cell_map(
+          masm->isolate()->heap()->global_property_cell_map());
+      __ Cmp(rbx, undefined_sentinel);
+      __ j(equal, &okay_here);
+      __ Cmp(FieldOperand(rbx, 0), global_property_cell_map);
+      __ Assert(equal, "Expected property cell in register rbx");
+      __ bind(&okay_here);
+    }
   }
 
   if (FLAG_optimize_constructed_arrays) {
     Label not_zero_case, not_one_case;
     __ testq(rax, rax);
     __ j(not_zero, &not_zero_case);
     ArrayNoArgumentConstructorStub no_argument_stub;
     __ TailCallStub(&no_argument_stub);
 
     __ bind(&not_zero_case);
@@ skipping 325 matching lines @@
   Deoptimizer::EntryGenerator generator(masm, Deoptimizer::OSR);
   generator.Generate();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64